Atomizing device for oil burners



Oct. 18, 1949. w. SANBORN ATOMIZING DEVICE FOR OIL BURNERS Filed Sept. 26, 1947 7 MW 1 W Patented Oct. 18, 1949 ATOMIZING nsvrcs ron on. nmmsns William L. Sunburn, Whitefish Bay, Wls., assignor to Sanborn Systems, Inc., a corporation of Wisconsin Application September 26, 1947, Serial No. 776,233

4 Claims- (Cl. 158-76) This invention relates to gun type oil burners for use in automatic oil firing. Oil burner of both the low-pressure and high-pressure atomizin types have an air tube for conducting the fan air into the firebox. This air tube surrounds the oil feed pipe and the ignition equipment and discharges the air slightly beyond the nozzle tip. If the air from the blower was permitted to flow into the firebox in whatever path it might naturally tend to follow under the existing conditions, the mixture of air and fuel would be ineifective and the resultant flame inefficient and poorly for-med. For this reason, baffles and vanes are used in the air tube in an effort to direct the air stream in a manner that will yield well formed flames having solidity and inducing a turbulence to promote efficient combustion.

Heretofore, however, those things have been only partially successful; and in what may be called the standard arrangement, consisting of a few fins around the inner circumference of the air tube, only about one-third of the secondary air is really controlled and the remainder shoots down the center of the flame, blowing the atomized oil away from the nozzle, causing pulsating flames and resulting in poor mixture and smoke puffs.

The principal object of this invention is to overcome the shortcomings of the prior devices and give complete control of the air in automatic oil firing, not only delivering ample air into the atomizing oil and flame but feeding auxiliary air inwardly across the nozzle, wiping it clean, preventing carbonizing, breaking the partial vacuum which ordinarily exists ahead of the nozzle, and drawing the suspended flame closer and making it steadier. As a result, combustion is more complete, and the efficiency of the burner is corre spondingly increased.

Other objects and advantages of the invention will appear as the disclosure proceeds and the description is read in connection with the accompanying drawings, in which Fig. 1 is a longitudinal section through an oil burner embodying the invention; and

Fig. 2 is a perspective view showing the swirler embodying the invention applied to the nozzle head of a burner.

Generally speaking, the objects of the invention are accomplished by providing a swirler mounted upon the nozzle head including a plurality of sector shaped vanes set at an angle normal to the axis of the nozzle between the head of the nozzle and the air tube for directing the main body of secondary air and providing each 2 vane adjacent to its inner portion with a slot extending from the forward edge approximately half way, thereby providing auxiliary air passages in circular series about the nozzle head to direct several streams of air across the face of the nozzle into the partial vacuum, thereby supplying ample air at all points in the flame zone including those ,which have heretofore received an inadequate supply, particularly high pressure atomizing gun type burners.

In the drawings, there is shown an oil feed pipe l0 equipped with a nozzle head II having a rounded face l2 by which the oil is supplied and atomized. Fixed to the pipe I0 is a bracket l3, which supports the ignition apparatus including electrodes II. An air tube l5 surrounds the described apparatus and serves to deliver the air from a blower (not shown) into the furnace at the right in Fi 1.

It is within this air tube l5 that baflles and vanes have heretofore been used in an effort to control and direct the air in a manner that would yield well formed flames and promote the desired combustion. According to this invention, those baflles and vanes are entirely dispensed with. To perform the desired function, the invention includes what will be called a swirler, generally indicated by the letter S.

The swirler consists essentially of a disk of thin sheet metal, such as 18 gauge galvanized steel for example, slit and formed up to produce an annular ring-like hub l6 and segmental outwardly extending vanes I! in circular series about the hub in fan-like arrangement at corresponding acute angles to a plane normal to the axis of the hub 15.

In the form here illustrated, the disk has been slit along radial lines defining the edges 18 and IQ of the segmental vanes, and also at the perimeter of the hub l6 each vane ha been slit from what will be called the right edge I9 inwardly about half way, as indicated at 20. After this, the vanes are twisted to set them at acute angles to a plane normal to the axis of the hub, in which position they serve to direct the air into a twisting spiral flow which slips off the broad right or forward edges of the vanes, producing a churning whirl of air immediately embracing and blending with the finely atomized oil mist.

The twisting also opens up slots corresponding to the slits 20, which, to av01d confusion, will be given the same reference numeral, and those slots provide the auxiliary air passages in circular series about the nozzle head, thereby producing, with the aid of the partial vacuum swift streams 3 bending and sweeping across the face of the nozzle into the spray of oil mist; breaking the vacuum and supplying vitally needed air at the heart of the combustion and flame zone.

The swirler may have six, eight, ten, twelve or more segments, but at present eight appears to ive the best results.

They may be given a variety of angles-for example from 15 to 60 degrees-but it appears now that about 45 degrees will ordinarily give the desired result. They, of course, may be made in various sizes to suit the. particular size of burner, but, in general, they should allow sumcient clearance between their circumference and. the inside of the air tube It to permit ready insertion and removal of the nozzle assembly into and from the air tube. Preferably also, at least the forward portions of the vanes fit snugly against the inner inclined face of a cone 2|, which has a press flt with the forward end 22 of the air tube. The inclined face of the cone 2|, together with the action of the vanes causes the air passing through the air tube to be delivered in a swirling, slightly converging manner. The slope of the cone may vary, but it now appears that about 30 degrees will give satisfactory results in most sizes.

Another feature of the invention especially useful in large burners is the auxiliary air tube 25 surrounding the air tube I5 with a clearance of one-half to three-quarters of an inch, or otherwise sufficient to permit a good flow of air to be induced by the jet action of the main discharge through the pipe |5. This air induction tube will supply a large additional quantity of air to improve the combustion and increase the capacity of the burner, and is adjustable lengthwise of the tube to vary the amount of induced air.

Preferably, the tube 25 is provided with a cone 28, substantially as shown in Fig. 1, to direct the additional air toward the heart of the combustion.

Providing the auxiliary air tube 25 results in a desirable cooling effect not only during the period of operation but during the shut-down periods when the refractory heat appears to drift back into the burner and its accessories. In this connection, the swirler with its vanes l1, spread across the mouth of the air tube l5, acts to absorb the refractory heat and dissipate it through the convection of currents of air that naturally pass along the air tube l5 duripg shut-down periods.

The hub ring I8 is welded or otherwise made fast to a substantial hub 28 provided with a set screw 29 to make it fast upon the nozzle head.

The reference to making the swirler of 18 gauge galvanized steel, or some other like strong metal, is not intended to exclude the use of special heat resisting and radiating alloys and other materials, many of which are most conveniently made by casting. The slitting along radial lines to form the sector shaped vanes and along the lines 20 to form the slots is illustrative only, and designers will change those lines to vary the form of the passages between the vanes and through the slots 20 to suit the particular needs of various situations, in some of which sharp corners will be rounded to reduce resistance and contribute to the speed of the swirling streams of air directed into the oil mist and the combustion zone, and, in particular, directing the streams indicated by the arrows 21 through the slots 20 and sweeping inwardly across the 4 face of the node into the partial vacuum created before it. a

The relation between the swirler and the nozzle shown in the drawing appears to give the optimum results, from which it seems that the nozzle should be approximately flush with the forward edges I. of the swirler vanes. It has been successfully placed behind that plane, but so far it has not been very satisfactory in front of that position. Also, the relation between the cone 2| and the nozzle shown in the drawing appears to give the best results. For example, with an air tube 4" in diameter and a cone tapering to 3" in diameter at the outlet, the face of the nozzle should be about 1" within the outlet of the cone.

Tests have shown that for most gun type burners, the CO: readings may be increased by 3 to 5% using the teachings of the invention. and in some cases the CO: readings can be brought to as high as 14%%.

I claim:

1. In combination with an oil burner of the gun type having an oil feed line terminating in a nozzle with an air tube telescoped thereover, a swirler comprising a hub mounted on and secured to the oil feed line immediately to the rear of the nozzle, a plurality of radial vanes mounted on the hub and angularly disposed relative to a plane normal to the axis of the hub, and means adjacent to the hub for directing a portion of the air passing through the swirler radially inwardly to converge upon the axis of the hub to thereby provide a stable burner flame close to the nozzle and sweep over the nozzle to keep it clean, said means including a plurality of slots extending circumferentially about the hub and defined at their outer margins by the angularly disposed vanes.

2. In combination with an oil burner of the gun type having an oil feed line terminating in a nozzle with an air tube telescoped thereover, a swirler comprising a hub mounted on and secured to the oil feed line immediately to the rear of the nozzle, a plurality of radial vanes mounted on the hub and angularly disposed relative to a plane normal to the axis of the hub, and means adjacent to the hub for directing a portion of the air passing through the swirler radially inwardly to converge upon the axis .of the hub to thereby provide a stable burner flame close to the nozzle and sweep over the nozzle to keep it clean, said swirler being formed from a flat sheet of metal having a plurality of slots extending circumferentially about the hub and radially slit to define said vanes.

3. An air swirler for oil burners of the gun type having an oil feed line terminating in a nozzle with an air tube telescoped thereover, said swirler comprising a hub adapted to be mounted on and secured to the oil feed line immediately to the rear of the nozzle, a plurality of radial vanes mounted on the hub and angularly disposed relative to a plane normal to the axis of the hub with the rear edges of the vanes lying substantially in said plane, and means adjacent to the hub for directing a portion of the air passing through the swirler radially inwardly to converge upon the axis of the hub, said means including a plurality of slotsextending circumferentially about the hub and defined at their outer margins by the angularly disposed vanes.

4. An air swirler for oil burners of the gun type having an oil feed line terminating in a nozzle with an air tube telescoped thereover, said swirler emu.

I comprising a. hub adapted to be mounted on and secured to the oil feed line immediately to the rear of the nozzle, a plurality of radial vanes mounted on the hub and angularly disposed relative to a plane normal to the axis of the hub with the rear edges of the vanes lying substantially in said plane, and means adiacent to the hub for directing a portion of the air passing through the swirler radially inwardly to converge upon the axis of the hub, said swirler being formed from a flat sheet of metal having a plurality of slots extending circumferentially about the hub and radially slit to define said vanes.

' WILLIAM L. SANBORN.

REFERENCES CITED The following references are of record in the tile of this patent:

Number Number UNITED STATES PATENTS Name Date Reif et al June 12, 1928 Stillman July 2, 1929 Hammer Jan. 28, 1930 Williams Nov. 10, 1931 Glanola Oct. 5, 1937 Chadima et al. Feb. 20, 1940 Hirtz et al Nov. 5, 1940 Stillman Oct. 21, 1941 Schwartz Aug. 11, 1942 Glendenning Jan. 29, 1946 FOREIGN PATENTS Country Date Great Britain Jan. 8, 1931 France Nov. 18, 1938 

